This is the text of Allan Bloom, see at JSTOR:

"Review: Justice: John Rawls Vs. The Tradition of Political Philosophy: A Theory of Justice by John Rawls
Reviewed Work: A Theory of Justice by John Rawls
Review by: Allan Bloom
The American Political Science Review
Vol. 69, No. 2 (Jun., 1975), pp. 648-662
Published by: American Political Science Association
DOI: 10.2307/1959094
Stable URL: http://www.jstor.org/stable/1959094
Page Count: 15"

The previous reviewer is correct.

This is not a work by Habermas, but a review of Rawls' "A Theory of Justice" by Allan Bloom, which appeared in a 1975 edition of The American Political Science Review the Justice.

See: http://www.jstor.org/stable/1959094

This supposed unpublished lecture is quite funny and recommend it even if it as far I can see it is nothing but a HOAX. The lecture is not listed anywhere and the tone of the text is not usual of Habermas at all. Until someone provides evidence that this lecture is authentic I would seriously doubt quoting it. The bottom line is that most of the criticisms or plain jokes that the text has are not to be found in the other text where Habermas critique's Rawls so I think it is a Hoax. Prove me wrong though, it would be nice.